Field of the Invention
The present invention relates to a touch sensing system, and more specifically, to a touch sensing system to which touch input can be applied through an active stylus pen and a driving method thereof.
Discussion of the Related Art
User interfaces (UIs) enable people (users) to easily control various electronic devices as desired. Typical examples of such UIs include a keypad, a keyboard, a mouse, an on-screen display (OSD), a remote controller having an infrared communication or radio frequency (RF) communication function, etc. User interface technology steadily develops to increase user emotion and operation convenience. Recent user interfaces have evolved into a touch UI, a speech recognition UI, a 3D UI and the like.
The touch UI is essentially adopted by portable information devices. The touch UI is implemented through a method of generating a touchscreen on a screen of a display device. The touchscreen may be a capacitive touchscreen. A touchscreen having a capacitive touch sensor detects touch input by sensing a capacitance variation according to input of a touchscreen driving signal, that is, a charge variation in a touch sensor, when a finger or a conductive material contacts (or approaches) the touch sensor.
The capacitive touch sensor may be configured as a self-capacitance sensor or a mutual capacitance sensor. Electrodes of the self-capacitance sensor can be connected one-to-one to sensor lines formed in one direction. The mutual capacitance sensor can be formed at an intersection of sensor lines intersecting each other having a dielectric layer interposed therebetween.
Recently, a stylus pen as well as a finger have been widely used as a human interface device (HID) for smartphones, tablets and the like. The stylus pen has the advantage of more precise input than a finger. There are passive and active stylus pens. The passive stylus pen has difficulty detecting a touch point because capacitance slightly varies at a touch point on a touchscreen. The active stylus pen generates a pen driving signal and outputs the pen driving signal to a touch point on a touchscreen and thus easily detects a touch point compared to the passive stylus pen.
Recent active stylus pens have been designed to transmit various additional pen information, such as pen pressure information, button state information and pen ID information, as well as the pen driving signal. However, a conventional active stylus pen further requires an additional communication block for transmitting additional pen information to a touch module, as disclosed in Korean Patent No. 10-2014-0043299, increasing manufacturing costs. Furthermore, the conventional active stylus pen has large transmission load because a pen driving signal and additional pen information are individually transmitted. To solve this problem, a method of loading the additional pen information on the pen driving signal and the pen driving signal including the additional pen information on the basis of touch frames may be considered. To this end, the active stylus pen needs to discriminate touch frames but methods therefor have not yet been developed.